SPID#: 43 As part of ongoing studies directed to identification of potential male contraceptives and to greater understanding of basic reproductive physiology of the chimpanzee, we have used tissues obtained from reproductively normal chimpanzees at time of necropsy and have conducted PCR and Northern Blot analyses to identify messages for five epididymis specific proteins (EPI-1-EPI-5) thought to have a potential function in induction and maintenance of sperm fertilizing capacity. We have subcloned and sequenced PCR fragments for EPI-1 - EPI-3 and demonstrated that they have the expected sequences. We have used subcloned fragments for EPI-1 and EPI-2 as probes for Northern analysis. Using Northern analysis message for EPI-1 was detected in chimpanzee epididymis and not testis, kidney or uterus. EPI-2 was also detected in epididymis but not testis, kidney or uterus. Using subdivided epididymis, it appears that EPI-1 and EPI-2 are synthesized in the posterior portion of the caput epididymis. Using antibodies generated in the rabbit, EPI-1 has been shown to have an effect on fertilization as demonstrated by reduction in the success of the Sperm Penetration Assay (SPA) using hamster oocytes when antibody to EPI-1 is present. The precise function of this protein in fertilization is currently under study. These studies will provide information applicable to maintenance of the captive chimpanzee population and results will be directly applicable to the human.